JP2002100837A - Nitride semiconductor light-emitting element and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nitride semiconductor light-emitting element, having few crystal defects and superior characteristics. SOLUTION: In a nitride semiconductor light-emitting element, having a structure consisting of a plurality of layers 102-112 made of a nitride semiconductor on a GaN substrate 101, a transition inhibiting layer 104 consisting of a nitride semiconductor and having carbon, is included between a luminescent layer 107 and a substrate 101. The transposition inhibiting layer 104 is an AlGaN layer containing carbon with the density of 1014 cm3-1020 cm-3. The thickness of the transition inhibiting layer 104 is 40 nm-0.7 μm. The transition inhibiting layer 104 can effectively prevent the generation of transition caused by lattice mismatch between an n-type GaN layer 102 and an n-type AlGaN clad layer 103.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nitride semiconductor light emitting device and a method of manufacturing the same, and more particularly, to a nitride semiconductor light emitting device having high luminance and a method of manufacturing the same.

[0002]

2. Description of the Related Art Light emitting devices and high power devices using nitride semiconductors have been researched and developed. By adjusting the composition of the nitride semiconductor, it is possible to cope with various applications. For example, in the case of a light-emitting element, a light-emitting element can be obtained in a wide range from blue to lantern. Light emitting diodes and green light emitting diodes have been put to practical use. Further, blue-violet semiconductor lasers are being developed. The structure of such a light emitting element is G
It is manufactured by homoepitaxially or heteroepitaxially growing a nitride semiconductor crystal film on a substrate made of aN, sapphire, SiC, ZnO, CaO, MnO, or the like. However, for example, when heteroepitaxial growth is performed, crystal defects such as dislocations occur due to lattice mismatch existing between the substrate and the epitaxially grown film, and the characteristics of the device deteriorate.

[0003] Regarding the problem of the lattice mismatch, Japanese Unexamined Patent Publication No.
Japanese Unexamined Patent Publication No. 220173 discloses that In _a Ga _1-a N (0 <a ≦
1) film, or consist of any of _{Al b Ga 1-b N (} 0 <b ≦ 1) film or a different Al _b Ga _1-b N compositions (0 ≦ b ≦ 1) multi-layer film formed by laminating thin films, A gallium nitride-based compound having a structure in which a second n-type gallium nitride-based compound semiconductor layer is sandwiched between a first n-type gallium nitride-based compound semiconductor layer and a third n-type gallium nitride-based compound semiconductor layer A semiconductor light emitting device is disclosed. In this structure, the second n
It is described that a gallium nitride-based compound semiconductor layer acts as a buffer layer and can reduce crystal defects. Japanese Patent Application Laid-Open No. 11-162847 discloses that a second buffer layer is deposited on a nitride semiconductor layer heteroepitaxially grown on a substrate via a low-temperature buffer, and energy is applied to the buffer layer to cause single crystallization. After that, a method of obtaining a nitride semiconductor layer with a low defect density by performing a necessary number of times of growing a nitride semiconductor layer again thereon is disclosed.

[0004]

However, in any of the above-mentioned prior arts, after taking measures to reduce crystal defects, one layer of a nitride semiconductor layer having a different composition, for example, a layer newly containing A1 is further added. If the above layers are stacked, a new lattice mismatch occurs between the layer and the layers before and after the layer,
Dislocations may be generated from the layer, and the quality of each layer thereafter may deteriorate. For example, a GaN film having a low defect density is manufactured using the above-described prior art, and an A for optical confinement is formed thereon.
When an lGaN cladding layer is formed, dislocations are newly generated due to lattice mismatch between the cladding layer and a layer adjacent thereto. When an active layer composed of multiple quantum wells is grown thereon, the active layer is formed on the surface with increased unevenness, resulting in a loss of the steepness of the well layer / barrier layer constituting the multiple quantum well. In addition, the characteristics of the active layer deteriorate. In particular, in the case of a laser element, if dislocations are present in the element, the life of the element is adversely affected by proliferation and spiral movement. If the Al-containing layer exists below the active layer during the growth of the device structure, the quality of the active layer may be adversely affected. A1 in the AlGaN cladding layer
When the composition ratio exceeds 0.1, cracks are remarkably generated in the process of growing a thin film on the thin film, and the yield of the device manufacturing and dividing steps may be reduced.

An object of the present invention is to provide a technique capable of suppressing dislocations that may newly occur during formation of an element structure.

It is a further object of the present invention to provide a nitride semiconductor light emitting device having few crystal defects and exhibiting excellent characteristics, and a method of manufacturing the same.

[0007]

Means for Solving the Problems The present inventors have found that a nitride semiconductor layer containing carbon can prevent the generation of new dislocations as described above, and have completed the present invention.

Thus, according to the present invention, there is provided a nitride semiconductor light emitting device having a structure in which a plurality of layers made of a nitride semiconductor are formed on a substrate, wherein the light emitting layer is formed between the light emitting layer and the substrate. Further, there is provided a nitride semiconductor light emitting device comprising a dislocation blocking layer made of a nitride semiconductor and containing carbon.

In one preferred embodiment of the present invention, a first layer made of a nitride semiconductor and a first semiconductor made of a nitride semiconductor containing an element different from the first layer are provided between the light emitting layer and the substrate. A plurality of second layers closer to the light emitting layer than the second layer, and the dislocation blocking layer includes a plurality of second layers.
Are provided between the layers. The thickness of the second layer is 0.7
It is preferably not more than μm.

In another preferred embodiment of the present invention, a first layer made of a nitride semiconductor and a nitride semiconductor containing an element different from the first layer are provided between the light emitting layer and the substrate. A second layer closer to the light emitting layer than the first layer is provided, and the dislocation blocking layer is provided between the second layer and the light emitting layer or in the second layer.

In the present invention, for example, the first layer is made of a nitride semiconductor containing no Al, and
Is made of a nitride semiconductor containing Al.

In the present invention, the dislocation blocking layer contains 1 carbon.
It is preferable to contain it at a concentration of 0 ¹⁴ / cm ³ or more and 10 ²⁰ / cm ³ or less.

In the present invention, the dislocation blocking layer is preferably
It preferably has a thickness of 0 nm or more and 0.7 μm or less.

[0014] Typically, the nitride semiconductor constituting the nitride semiconductor light-emitting device of the present invention have the general formula In _x Ga _y Al
_{1- (x + y)} N is a nitride semiconductor represented by N (0 ≦ x ≦ 1, 0 ≦ x + y ≦ 1).

Further, according to the present invention, there is provided a method for manufacturing the above-mentioned nitride semiconductor light emitting device. The method comprises forming a plurality of layers of a nitride semiconductor including a dislocation blocking layer and a light emitting layer on a substrate. Forming a dislocation blocking layer at a temperature of 500 ° C. or more and 1100 ° C. or less.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a layer made of a nitride semiconductor and containing carbon reduces dislocations newly generated from, for example, a layer containing A1, and further reduces stress in the layer by cracking. To prevent the occurrence of
The characteristics of the light-emitting element can be improved. Typically,
In the present invention, the dislocation blocking layer is provided between the light emitting layer (active layer) for generating light emission and the substrate. In a light-emitting element structure formed over a substrate, the dislocation blocking layer according to the present invention is generated by stacking a second layer made of a nitride semiconductor containing an element different from the first layer on the first layer. Possible dislocations can be prevented. For example, the first layer has a general formula of In _x Ga _1-y N (0 ≦ x <1, 0 ≦ y <1)
In represented by a nitride semiconductor, the second layer, the general formula _{In x Ga y Al 1- (x} + y) N (0 ≦ x ≦ 1,0 ≦ y <1,
It is made of a nitride semiconductor containing Al represented by 0 <x + y <1). In the present invention, the first layer and the second layer are
Typically, between the substrate and the light emitting layer. A plurality of second layers may be provided on the first layer. Typically, the dislocation blocking layer is provided between the second layer and the light emitting layer, or provided between a plurality of second layers. The dislocation blocking layer may be provided in contact with the second layer, or may be provided in contact with another layer formed over the second layer. For example, the first layer can be a GaN layer and the second layer can be AlG
An aN layer can be used, and the dislocation blocking layer can be an AlGaN layer containing carbon as an impurity. In this case, the dislocation blocking layer may be provided in contact with the second layer, or may be provided on another layer which is in contact with the second layer. The dislocation blocking layer includes a plurality of second dislocation blocking layers formed on the first layer.
May be provided between the layers. In this case, for example, the first layer can be a GaN layer, and the plurality of second layers are Al
The dislocation blocking layer may be an AlGaN layer containing carbon as an impurity. Also,
The first layer is a GaN layer, and the second layer is a GaN thin film and Al
A super lattice structure in which N thin films are stacked may be used. When the second layer has such a superlattice structure, carbon can be contained as an impurity in the GaN thin film constituting the superlattice, and can function as a dislocation blocking layer. For example, in the present invention, the first layer can be an n-type nitride semiconductor layer, and the second layer can be a clad layer made of an n-type nitride semiconductor. Further, the first layer may be an n-type nitride semiconductor layer, and the plurality of second layers may be clad layers. Further, the first layer may be an n-type nitride semiconductor layer, and the second layer may be a cladding layer made of a dislocation blocking layer and an n-type nitride semiconductor.

The device according to the present invention can be obtained, for example, by hetero- or homoepitaxially growing a plurality of nitride semiconductor films on a substrate made of sapphire, SiC, GaAs, spinel, GaN or the like. Usually, first, thermal cleaning is performed at a high temperature of 1000 ° C. or more in a hydrogen atmosphere, then a buffer layer is formed at about 500 ° C., and then a nitride semiconductor layer is epitaxially grown at about 1050 ° C. to form a light emitting element structure. I will do it. In this process, for example, 1 carbon is added between the layer containing A1 and the light emitting layer or inside the layer containing A1.
Thickness 50 including a concentration of 0 ¹⁴ cm ^-3 or more and 10 ²⁰ cm ^-3 or less
It is preferable to insert a dislocation blocking layer having a thickness of not less than nm and not more than 0.5 μm. By inserting a dislocation blocking layer to which carbon is added below the light emitting layer and above the layer containing A1,
During the manufacture of the element structure, dislocation generated from the interface between the layer containing A1 and the other layers can be effectively prevented from propagating to the light emitting layer, and the element characteristics can be improved. For example, metal organic chemical vapor deposition (MOCV)
D), a method generally used for growing nitride semiconductor crystals, such as molecular beam epitaxy (MBE) or hydride vapor phase epitaxy (HVPE), can be applied. In consideration of productivity, the MOCVD method, which is lower in cost than other methods and can use a large area substrate, is most suitable.

FIG. 1 shows an example of a laser device according to the present invention. Each layer constituting the element is grown by, for example, the MOCVD method. In this laser device, an n-type GaN layer 102, a first n-type AlGaN cladding layer 103 for confining light, a dislocation blocking layer 104, and a second n-type AlGaN cladding layer are sequentially formed on an n-type GaN substrate 101. 10
5. N-type GaN light guide layer 106 for distributing light near the active layer, InGaN multiple quantum well active layer (light emitting layer) 107, prevention of sublimation of the active layer during the device structure manufacturing process and diffusion of impurities from the p-type layer To prevent AlGaN
A block layer 108, a p-type GaN light guide layer 109, a p-type AlGaN cladding layer 110, a p-type GaN layer 111, and a p-type GaN contact layer 112 are formed.
For example, the dislocation blocking layer 104 is an AlGaN layer containing carbon for preventing dislocations and cracks generated from the n-type AlGaN cladding layer. P-type Ga in the top layer
The N layer 112 is processed into a ridge shape to confine light in the lateral direction. The insulating film 1 is formed on the p-type GaN layer 112.
13 is formed by ordinary photolithography, and a p-type electrode 114 is further provided. The substrate 10
An n-type electrode 115 is formed on the back surface of 1. The substrate, in addition to GaN, sapphire, SiC, GaAs, spinel (MgA1 ₂ O ₄₎ or the like, generally may be used nitride semiconductor crystal can be grown material thereon. in this way,
When the conventional n-type AlGaN cladding layer is divided into two and the dislocation blocking layer 104 to which carbon is added is inserted between the two, the dislocation generated at the time of growing the first n-type AlGaN cladding layer 103 is as follows. Due to the carbon clusters formed inside the dislocation blocking layer 104, the second n-type AlGa
Propagation to the N cladding layer 105 is prevented. By this action, the density of dislocations penetrating the n-type light guide layer 106 and the multiple quantum well active layer 107 stacked on the second n-type AlGaN cladding layer 105 is significantly reduced as compared with the conventional structure, and the n-type GaN Since the surface of the light guide layer 106 is flattened, the steepness between the layers of the multiple quantum well active layer 107 can be improved. Also, n-type AlGaN
By dividing the clad layer into two layers, the stress inside the clad layer is reduced, and it is possible to prevent cracks that normally reach the element surface.

According to the present invention, in the size of a general laser element, the number of dislocations that can be present in the current-carrying region of the element can be one or less, and the dislocation density is practically negligible.
A dislocation density of × 10 ¹⁴ cm ⁻² or less can be realized. On the other hand, when the dislocation blocking layer was not provided, due to the effect of dislocation newly generated due to the lattice constant difference between the n-type AlGaN cladding layer and the other layers, the thickness of the periodic layer of the multiple quantum well active layer 107 was almost the same. Irregularities and micropipes may occur. In this case, the steepness of the barrier layer and the well layer constituting the multiple quantum well active layer 107 may be impaired. As a result, the quantum efficiency at the time of current injection decreases, and the device characteristics may deteriorate. Thus, by applying the present invention to a laser device, dislocations penetrating the active layer can be reduced, and cracks reaching the device surface can be significantly reduced. As a result, according to the present invention, characteristics such as light emission characteristics, drive voltage, drive current, and device life can be improved.

Generally, in the crystal growth of a nitride semiconductor,
Sapphire, SiC, GaN, GaAs, spinel, etc. are used as the substrate. Also, the crystal growth is performed by MOCV
D, MBE, HVPE. Considering the growth rate, cost and productivity of nitride semiconductors, it is preferable to use sapphire or GaN as the substrate, and MOCVD is generally used to fabricate device structures due to crystal quality and controllability of thin films. Is preferred.

The device according to the present invention was manufactured using, for example, a crystal growth apparatus shown in FIG. MOCV shown in FIG.
In the D apparatus, 701 is a GaN substrate or (000
1) A substrate made of surface sapphire or the like, and a carbon susceptor 7
02. In the susceptor 702, a heater for resistance heating, also made of carbon, is arranged, and the temperature of the substrate can be monitored and controlled by a thermocouple. 703 is a water-cooled reaction tube made of double quartz. As the group V raw material, ammonia 706 was used,
Group III raw materials include trimethylgallium (TM
G), trimethylaluminum (TMA), and trimethylindium (TMI) (709a to 709c) are used by bubbling with nitrogen gas or hydrogen gas. Also, n
Using SiH ₄ 707 as a doping material for
Biscyclopentadienyl magnesium (Cp ₂ Mg) 709d is used as a doping material for the mold.
Methane (CH ₄ ) 7 as a carbon source added to the dislocation blocking layer
08 is used. Each raw material is supplied to the mass flow controller 71
At 0, the flow rate is controlled accurately, and the raw material is introduced into the reaction tube 703 from the inlet 704 and discharged from the exhaust gas outlet 705. Hereinafter, specific examples of the laser device according to the present invention manufactured using the above-described apparatus will be further described.

Example 1 A laser device was manufactured on a (0001) plane GaN substrate as shown below. In this example, two n-type AlGaN cladding layers were formed, and a dislocation blocking layer to which carbon was added was disposed between them. Hereinafter, the manufacturing method will be described with reference to FIGS.

First, a 400 μm-thick 5.08 cm (2
The (inch) diameter (0001) plane GaN substrate 101 is cleaned by an ordinary method and set in a MOCVD apparatus. The substrate is heated in an ammonia atmosphere and stabilized at 1050 ° C. After that, about 50 μmol / min of TMG and about 10 nmol / min of SiH ₄ gas are supplied to the n-type GaN layer 102.
Grow about 4 μm. Subsequently, TMA was added to 10 μmo
1 / min and the first n-type A1 having a thickness of 0.2 μm.
_{A 0.15} Ga _0.85 N cladding layer 103 is grown and SiH ₄
Stopping only, the Al _0.15 Ga _0.85 N dislocation blocking layer 104 is grown to a thickness of 0.1 μm while supplying CH ₄ at 10 nmol / min. At that time, it may be used general formula C _n H 2 carbon compound represented by _{(n +1),} or a carbon compound represented by _{C (C n H 2n + 1} ) 4. Stop CH ₄ , and again use SiH ₄
Is supplied at 10 nmol / min to grow the second n-type A1 _0.15 Ga _0.85 N cladding layer 105 to a thickness of 0.3 μm, and then the supply of TMA is stopped. Here, the first and second n-type cladding layers may or may not include carbon, but the concentration when carbon is included must be lower than 10 ²⁰ cm ⁻³ . This is because excess carbon becomes a new dislocation source. After growing the second cladding layer, about 0.1
A μm n-type GaN light guide layer 106 is grown. The light guide layer may or may not contain carbon, but in order to prevent excess carbon from becoming a dislocation source, the concentration when carbon is contained must be lower than 10 ²⁰ cm ^-3 . In order to grow the active layer 107 composed of multiple quantum wells, S
Stop supply of iH ₄ and TMG, and raise substrate temperature to 850 ° C
To about 800 ° C. Here, the growth temperature of the active layer and the supply amount of the group III raw material are one of the parameters that determine the emission wavelength of the device. If the supply amount of the group III raw material is the same, the emission wavelength tends to increase at a low temperature. . The substrate temperature is a temperature for producing a violet to green light emitting element, and can be changed according to a necessary wavelength band. After the temperature is stabilized, TMG is reduced to 10 μmo1 / mi.
n and TMI are supplied at 10 μmo1 / min, and the active layer 10 is supplied.
The In _0.05 Ga _0.95 N barrier layer forming 7 is grown to a thickness of about 5 nm. At that time, SiH ₄ was added at 10 nmo1 / m
The flow may be about in. Subsequently, TMG was added to 10 μmol
/ Min and TMI of 50 μmol / min are supplied, and In _0.2 Ga _0.8 N as a well layer is grown to a thickness of about 3 nm. The growth process of the barrier layer and the well layer is repeated to grow a multiple quantum well of a required period, and finally, the growth of the active layer 107 is completed by growing the barrier layer. In general, it has been found that when the number of well layers is changed from two to five, carriers can be most easily injected, and an element having high luminous efficiency can be obtained. Also, the active layer may or may not contain carbon, but if it does, the concentration must be lower than 10 ²⁰ cm ⁻³ . This is because excess carbon becomes a new dislocation source and increases the non-light emitting region in the active layer. After the growth of the active layer, TMG is applied to a thickness of 10 μmol to prevent sublimation of the InGaN film and diffusion of the dopant from the p-type layer on the active layer.
/ Min, TMA of 5 μmol / min, and Cp ₂
Mg is supplied to grow the AlGaN block layer 108 to a thickness of about 30 nm, and then TMG, TMA and Cp
The supply of ₂ Mg is stopped, and the temperature is raised again to 1050 ° C. After stabilizing the temperature, TMG was added to 50 μmol / min and C
Optical guide layer 1 made of p-type GaN by supplying p ₂ Mg
09 is grown 0.1 μm. Then, TMA was added to 10μ
mol / min and supply 0.5 μm p-type A1 _0.15 Ga
After growing the _0.85 N cladding layer 110, the supply of TMA is stopped, and the p-type GaN layer 111 is grown to about 4 μm. Finally, the supply amount of Cp ₂ Mg is doubled to make the p-type Ga
The N contact layer 112 is grown by 0.5 μm. After the completion of the entire growth process, the supply of TMG and Cp ₂ Mg is stopped, and the heating of the substrate is terminated. After cooling to room temperature, the substrate is removed and 900 ° C. in nitrogen at 10 ° C. to activate Mg.
Heat treatment for a minute. After the p-type treatment, the back surface is polished, and then photolithography and reactive ion etching (R
IE), a ridge having a width of 2 μm and a height of 0.4 μm is formed, and an insulating film 113 is formed by sputtering or electron beam (EB) so that only the top of the ridge is opened. 104 and an n-type electrode 115 on the rear surface, respectively. After the formation of the electrodes, the substrate is cleaved to form optical resonator end faces with a spacing of 500 μm.

For comparison, the AlGaN dislocation blocking layer 104 in FIG. 1 was omitted, and a laser device having a conventional structure shown in FIG. 2 was fabricated. In this device, the n-type GaN substrate 201
In order, n-type GaN layer 202 and n for optical confinement
-Type AlGaN cladding layer 203, n-type GaN light guide layer 204 for distributing light near the active layer, InGaN
Multiple quantum well active layer 205, AlGaN block layer 207, p-type GaN light guide layer 208, and p-type AlGaN cladding layer for preventing sublimation of the active layer and preventing diffusion of impurities from the p-type layer during the device structure manufacturing process 209, p-type G
An aN layer 210 and a p-type GaN contact layer 211 are stacked. The uppermost p-type GaN layer 211 is processed into a ridge shape to confine light in the lateral direction, and the insulating film 2 is formed.
12 is provided by ordinary photolithography. Further, a p-type electrode 213 is provided in an opening of the p-type GaN layer 211. On the back surface of the substrate 201, an n-type electrode 214 is formed. The thickness, impurity and concentration of each layer were adjusted to be the same as those of the corresponding layers in FIG.

When the device manufactured according to the above procedure was evaluated, the device having the conventional structure (FIG. 2) had an oscillation threshold current density of 800 A / cm ² at a voltage of 5 V, whereas the device added with carbon A
In the device in which the lGaN dislocation blocking layer is inserted (FIG. 1), a voltage of 4
At V, the oscillation threshold current density was 500 A / cm ² , indicating that both the driving voltage and the threshold current density were reduced by the dislocation blocking layer. Observation of the cross section of the device with a transmission electron microscope revealed that the conventional device had approximately 10 ⁶ / cm ^{2 of} dislocations penetrating the active layer. 10 ⁴ / cm ^{2 in} which less than one dislocation can exist in the region
It was confirmed that threading dislocations had been reduced. It is expected that the decrease in threading dislocations cuts off the path of current that does not contribute to light emission, thereby improving the carrier injection efficiency. Also, in the conventional device, the interface between the well layer / barrier layer of the multiple quantum well active layer is disturbed by irregularities and micropipes generated from the n-type AlGaN cladding layer, whereas in the device in which the carbon-doped AlGaN dislocation blocking layer is inserted, The first n
Generated from the AlGaN cladding layer is carbon-added A
Since the generation of irregularities and micropipes is suppressed at the same time as being blocked by the lGaN dislocation blocking layer, disturbance at the well layer / barrier layer interface of the multiple quantum well located above the second n-type AlGaN cladding layer is reduced. Was confirmed. It is considered that the light emitting efficiency of the active layer was improved due to the sharp formation of the well layer / barrier layer interface, and that the drive voltage and the oscillation threshold current density were reduced due to a synergistic effect with the improvement of the injection efficiency. In the conventional device, cracks occurred at intervals of about 1 mm on average, but in the device manufactured in this example, only a few cracks were observed around the sample.

Example 2 A laser device was manufactured on a (0001) sapphire substrate as shown below. In this embodiment, an AlGaN layer to which carbon is added is disposed between the n-type AlGaN cladding layer and the active layer. The manufacturing method will be described with reference to FIGS.

A 5.08 cm (2 inch) diameter (0001) plane sapphire substrate 301 having a thickness of 400 μm is cleaned by an ordinary method, set in an MOCVD apparatus, and cleaned in a hydrogen atmosphere at 1200 ° C. for 10 minutes. After that, the temperature was lowered to 500 ° C., and ammonia and TMG were supplied at about 50 μmol, and the GaN buffer layer 302 was cooled to 40 ° C.
It is formed with a thickness of nm. The buffer layer is not limited to GaN but has the general formula In _x A1 _y Ga _{1- (x + y)} N (x ≦ 1, x + y ≦ 1)
Can be used. After forming the buffer layer, the temperature was raised to 1050 ° C., and the n-type GaN layer 303, the first n-type AlGaN cladding layer 304, the carbon-added dislocation blocking layer 305, and the second n-type Al
GaN clad layer 306, n-type GaN optical guide layer 30
7, multiple quantum well active layer 308, carrier block layer 3
09, a p-type AlGaN cladding layer 310, a p-type GaN layer 311, and a p-type GaN contact layer 312 are sequentially grown. Adjustment of the thickness of each layer, impurities and their concentrations is the same as in the first embodiment. A first or second n-type cladding layer, n
The mold light guide layer and the active layer may or may not contain carbon, but if they do, the concentration must be lower than 10 ²⁰ cm ⁻³ . This is because excess carbon becomes a new dislocation source. After the growth, the sample was taken out from the MOCVD apparatus, Mg activation treatment and a ridge were formed in the same procedure as in Example 1, and the insulating film 313 and the p-type electrode 314 were formed.
Is deposited. Since sapphire is an insulator, the n-type GaN layer is exposed by RIE, and an n-type electrode 315 is deposited.

For comparison, a device having a conventional structure shown in FIG. 4 was prepared by omitting the carbon-added AlGaN dislocation blocking layer. In this device, G is sequentially placed on a sapphire substrate 401.
aN buffer layer 402, n-type GaN layer 403, n-type AlGaN cladding layer 404 for confining light, n-type GaN light guide layer 40 for distributing light near the active layer
5, an InGaN multiple quantum well active layer 406, an AlGaN block layer 407 for preventing sublimation of the active layer and preventing impurity diffusion from the p-type layer during the device structure fabrication process.
A GaN optical guide layer 408, a p-type AlGaN cladding layer 409, a p-type GaN layer 410, and a p-type GaN contact layer 411 are stacked. Uppermost p-type GaN layer 411
Is processed into a ridge shape to confine light in the lateral direction,
The insulating film 412 is provided by ordinary photolithography. Further, a p-type electrode 413 is provided in the opening. The n-type electrode 414 is formed on the n-type GaN layer 403 exposed by RIE. The adjustment of the thickness, the impurity and the concentration of each layer is the same as that of each corresponding layer in FIG.

When the device manufactured according to the above procedure was evaluated, the device of the conventional structure (FIG. 4) had an oscillation threshold current density of 1000 A / cm ² at a voltage of 6 V, and a carbon-added AlGaN dislocation blocking layer was inserted. In the device (FIG. 3), the oscillation threshold current density was 700 A / cm ² at a voltage of 5 V, and it was found that both the driving voltage and the threshold current density were reduced by the dislocation blocking layer. Observation of the cross section of the device with a transmission electron microscope revealed that the conventional device had approximately 10 ⁹ / cm ² dislocations penetrating the active layer, whereas the device with the carbon-added AlGaN dislocation blocking layer inserted therein had 10 ⁶ / cm 2. ^Two
It has been confirmed that the number has decreased. It is expected that the decrease in threading dislocations cuts off the path of current that does not contribute to light emission, thereby improving the carrier injection efficiency. Also, in the conventional device, the unevenness generated from the n-type AlGaN cladding layer and the micropipe make the well layer / multi-quantum well active layer.
Although the barrier layer interface is disturbed, carbon-added AlGaN
In the device in which the dislocation blocking layer is inserted, the first n-type AlGaN
Dislocations generated from the cladding layer are blocked by the carbon-added AlGaN dislocation blocking layer, and at the same time, the occurrence of irregularities and micropipes is suppressed.
It was confirmed that the disturbance at the well layer / barrier layer interface of the multiple quantum well located above the N cladding layer was reduced.
It is considered that the light emitting efficiency of the active layer was improved due to the sharp formation of the well layer / barrier layer interface, and that the drive voltage and the oscillation threshold current density were reduced due to a synergistic effect with the improvement of the injection efficiency. On the other hand, the conventional device has an average of 5
Although cracks occurred at intervals of about 00 μm, only a few cracks were observed around the sample in the device manufactured in this example. The same effect was confirmed when a different kind of substrate other than sapphire was used.

Example 3 A laser device was fabricated on a (0001) plane GaN substrate as shown below. In the present embodiment, A with carbon added between the n-type AlGaN cladding layer and the n-type GaN optical guide layer
An lGaN layer was arranged. The manufacturing method will be described with reference to FIGS.

First, a 400 μm thick 5.08 cm (2
Inch) diameter (0001) plane GaN substrate 501
After washing by the method, it is set in the MOCVD apparatus. Ann board
Heat in a monia atmosphere and stabilize at 1050 ° C. So
After that, TMG was added to about 50 μmol / min and SiH_Fourgas
Is supplied to the n-type GaN layer 502 by about 10 nmol / min.
Grow about 4 μm. Subsequently, TMA was added to 10 μmo
1 / min, n-type A1 with a thickness of 0.2 μm_0.15G
a_0.85The N cladding layer 503 is grown. Then, Si
H_FourStop only CH_FourSupply 10 nmo1 / min
One, A1_0.15Ga_0.85N dislocation blocking layer 504 is 0.1 μm
Grow to a thickness of At this time, the general formula C _nH_{2 (n + 1)}In table
Carbon compound, C (C_nH_{2n + 1})_FourCarbonization represented by
Compounds may be used. Here, the n-type cladding layer contains carbon.
It may or may not be included, but the concentration when carbon is included
Is 10²⁰cm^-3Must be lower. this is,
This is because excess carbon becomes a new dislocation source. Dislocation blocking
After layer growth, TMA and CH _FourStop, about 0.1 μm
The n-type GaN optical guide layer 505 is grown. Light guide
The layer may or may not contain carbon, but excess carbon
To prevent it from becoming a dislocation source,
Degree is 10²⁰cm^-3Must be lower. Multiple quantum
In order to grow the active layer 506 made of a well, SiH
_FourAnd supply of TMG are stopped, and the temperature of the substrate is set to 850 ° C.
Lower to about 800 ° C. After the temperature stabilizes, TMG
10 μmo1 / min, TMI 10 μmo1 / min
To form the active layer 506_0.05Ga_0.95N obstacles
The wall layer is grown to a thickness of about 5 nm. At that time, SiH_Four
May flow at about 10 nmo1 / min. Then T
MG 10 μmo1 / min, TMI 50 μmo1 /
min, and the well layer In_0.2Ga_0.8N is about 3n
grow to a thickness of m. Repeat the growth process of barrier layer and well layer
After growing multiple quantum wells with the required period,
Later, a barrier layer is grown to terminate the growth of the active layer 506.
You. Usually, the number of well layers is most preferably changed from two to five.
A device with good luminous efficiency that allows easy carrier injection
I know. The active layer also contains carbon
Although not necessary, the concentration when containing carbon is 10²⁰cm
^-3Must be lower. This is because excess carbon is new
Dislocation source and increase non-light emitting region in active layer
That's why. Sublimation and activity of InGaN film after active layer growth
To prevent dopant diffusion from the p-type layer on the layer,
TMG is 10 μmol / min, TMA is 5 μmol / min.
min, and Cp_TwoSupply Mg, about 30nm thickness
Then, an AlGaN block layer 507 is grown. TMG,
TMA and Cp_TwoThe supply of Mg was stopped, and
Heat to 0 ° C. After stabilizing the temperature, TMG 50 μm
o1 / min and Cp_TwoMg supply, p-type GaN
The light guide layer 508 is grown by 0.1 μm. Continued
And supply TMA at 10 μmo1 / min,
m p-type A1_0.15Ga_0.85The N cladding layer 509 is grown
Then, the supply of TMA is stopped, and the p-type GaN layer 510 is stopped.
Grow about 4 μm. Finally, Cp_TwoMg supply
Double the p-type GaN contact layer 511 to 0.5 μm
Let it grow. After completion of all growth steps, TMG and Cp_TwoMg
The supply is stopped to end the substrate heating. Cooled to room temperature
After that, take out the substrate and in nitrogen to activate Mg
A heat treatment is performed at 900 ° C. for 10 minutes. p-type processing
After polishing the back, photolithography and reactive ion
Width 2 μm and height 0.
Form a 4μm ridge and open only at the ridge top
The insulating film 512 is formed by sputtering or electron beam (EB) evaporation.
And a p-type electrode 513 in the opening on the top of the ridge, and
Each of the n-type electrodes 514 is deposited. After electrode formation,
Cleaving the substrate to form an optical resonator end face with a spacing of 500 μm
You.

For comparison, a device having a conventional structure shown in FIG. 2 was prepared by omitting the carbon-added AlGaN dislocation blocking layer.

When the device manufactured according to the above procedure was evaluated, the device having the conventional structure (FIG. 2) had an oscillation threshold current density of 800 A / cm ² at a voltage of 5 V, whereas the device added with carbon A
In the device in which the lGaN dislocation blocking layer was inserted (FIG. 5), the voltage was 3.9 V, the oscillation threshold current density was 440 A / cm ² ,
It was found that the introduction of the dislocation blocking layer lowered both the driving voltage and the threshold current density. Observation of the cross section of the device with a transmission electron microscope revealed that the conventional device had approximately 10 ⁶ / cm ² dislocations penetrating the active layer, whereas the device with the carbon-added AlGaN dislocation blocking layer inserted therein had 10 ⁴ / cm 2. ^It has been confirmed that it has decreased to ² . It is expected that the decrease in threading dislocations cuts off the path of current that does not contribute to light emission, thereby improving the carrier injection efficiency. Also, in the conventional device, the interface between the well layer / barrier layer of the multiple quantum well active layer is disturbed by irregularities and micropipes generated from the n-type AlGaN cladding layer, whereas in the device in which the carbon-doped AlGaN dislocation blocking layer is inserted, , N-type A
The dislocation generated from the lGaN cladding layer is carbon-added AlG
The interruption by the aN dislocation blocking layer and the suppression of the generation of the irregularities and the micropipes at the same time as the occurrence of the irregularities and the micropipes suppress the disorder of the well layer / barrier layer interface of the n-type optical guide layer and the multiple quantum well located above the dislocation blocking layer. It was confirmed that it was low. It is considered that the light emitting efficiency of the active layer was improved due to the sharp formation of the well layer / barrier layer interface, and that the drive voltage and the oscillation threshold current density were reduced due to a synergistic effect with the improvement of the injection efficiency. In the conventional device, cracks occurred at intervals of about 1 mm on average, but in the device manufactured in this example, only a few cracks were observed around the sample. The above effects are
The same could be confirmed when a heterogeneous substrate such as sapphire was used in addition to GaN.

Example 4 A laser device was manufactured on a (0001) plane GaN substrate as shown below. In this embodiment, an AlGaN layer to which carbon is added is disposed between the n-type GaN light guide layer and the active layer. The manufacturing method will be described with reference to FIGS.

First, a 400 μm-thick 5.08 cm (2
Inch) diameter (0001) plane GaN substrate 601
After washing by the method, it is set in the MOCVD apparatus. Ann board
Heat in a monia atmosphere and stabilize at 1050 ° C. That
Thereafter, TMG is added to about 50 μmol / min and SiH_FourGas
The n-type GaN layer 602 is supplied by supplying about 10 nmo1 / min.
Grow about 4 μm. Then, 10 μmol of TMA
/ Min at a thickness of 0.2 μm and n-type A1_0.15Ga
_0.85The N cladding layer 603 is grown. n-type cladding layer
May or may not contain carbon, but if it contains carbon
Is 10 ²⁰cm^-3Must be lower. This
This is because excess carbon becomes a new dislocation source. n
After growing the mold cladding layer, TMA and SiH_FourStop,
A n-type GaN optical guide layer 604 of about 0.1 μm is grown.
And restart the supply of TMA, and at the same time,_Four10 nmo
While supplying 1 / min, A1_0.15Ga_0.85N dislocation blocking layer
605 is grown to a thickness of 0.1 μm. At that time, general
Formula C_nH_{2 (n + 1)}A carbon compound represented by the formula: C (C_nH_{2n + 1})
_FourMay be used. Light guide layer
It may or may not contain carbon, but excess carbon is dislocated
To prevent carbon contamination, the concentration when carbon is contained
10²⁰cm^-3Must be lower. For dislocation blocking layer
Then, SiH_FourAnd supply of TMG are stopped, and the substrate temperature
Is reduced to about 850 ° C. to 800 ° C. Temperature stability
Thereafter, TMG is 10 μmo1 / min, TMI is 10 μm
o1 / min to form the active layer 606_0.05
Ga_0.95An N barrier layer is grown to a thickness of about 5 nm. That
, SiH_FourMay flow about 10 nmo1 / min
No. Next, TMG was set to 10 μmo1 / min and TMI was set to
50 μmo1 / min is supplied, and the well layer In_0.2G
a_0.8N is grown to a thickness of about 3 nm. Barrier layers and wells
Repeat the layer growth process to create multiple quantum wells with the required period.
After the growth, a barrier layer is finally grown to form the active layer 606.
To end the growth. The active layer may or may not contain carbon
However, when carbon is contained, the concentration is 10%.²⁰cm ^-3Than
Must be low. This means that the excess carbon
To increase the non-light emitting area in the active layer.
is there. After growing the active layer, sublimation of the InGaN film and
To prevent dopant diffusion from the p-type layer, TMG
10 μmo1 / min, TMA 5 μmo1 / mi
n and Cp_TwoMg is supplied, and A is formed to a thickness of about 30 nm.
The lGaN block layer 607 is grown. TMG, TM
A and Cp_TwoStop supplying Mg and return to 1050 ° C
Raise the temperature. After stabilizing the temperature, TMG50 μmo1 /
min and Cp_TwoLight consisting of p-type GaN by supplying Mg
The guide layer 608 is grown by 0.1 μm. Then, TM
A is supplied at 10 μmo1 / min, and 0.5 μm p-type A
1_0.15Ga_0.85After growing the N cladding layer 609, T
The supply of MA is stopped, and the p-type GaN layer 610 is reduced to about 4 μm.
Let it grow. Finally, Cp_TwoDouble the Mg supply
A p-type GaN contact layer 611 is grown by 0.5 μm.
You. After completion of all growth steps, TMG and Cp_TwoStop supplying Mg
Stop and terminate the substrate heating. After cooling to room temperature,
And 900 ° C. in nitrogen to activate Mg
For 10 minutes. After p-type treatment,
After polishing, photolithography and reactive ion etching
2 μm width and 0.4 μm height using RIE
An insulating film 6 is formed so that only the top of the ridge is opened.
12 by sputtering or electron beam (EB) deposition, and
A p-type electrode 613 is provided in the opening at the top of the device, and an n-type electrode
14 are each deposited. After electrode formation, cleave the substrate
In this way, an optical resonator end face having an interval of 500 μm is formed.

For comparison, a device having a conventional structure shown in FIG. 2 was prepared without the carbon-added AlGaN dislocation blocking layer.

When the device manufactured by the above procedure was evaluated, the device having the conventional structure (FIG. 2) had an oscillation threshold current density of 800 A / cm 2 at a voltage of 5 V, whereas the device added with carbon A
In the device in which the lGaN dislocation blocking layer is inserted (FIG. 6), a voltage of 4
At V, the oscillation threshold current density was 470 A / cm ² , and both the drive voltage and the threshold current density decreased. Observation of the cross section of the device with a transmission electron microscope revealed that the conventional device had approximately 10 ⁹ / cm ² dislocations penetrating the active layer, whereas the device with the carbon-added AlGaN dislocation blocking layer inserted therein had 10 ⁴ / cm 2. ^It has been confirmed that it has decreased to ² . It is expected that the decrease in threading dislocations cuts off the path of current that does not contribute to light emission, thereby improving the carrier injection efficiency. Also, in the conventional device, the interface between the well layer / barrier layer of the multiple quantum well active layer is disturbed by irregularities and micropipes generated from the n-type AlGaN cladding layer, whereas in the device in which the carbon-doped AlGaN dislocation blocking layer is inserted, , N-type A
The dislocation generated from the lGaN cladding layer is carbon-added AlG
It has been confirmed that the disturbance at the well layer / barrier layer interface of the multiple quantum well located above the dislocation blocking layer is reduced due to suppression of the occurrence of irregularities and micropipes while being blocked by the aN dislocation blocking layer. did it. It is considered that the light emitting efficiency of the active layer was improved due to the sharp formation of the well layer / barrier layer interface, and that the driving voltage and the oscillation threshold current density were reduced due to a synergistic effect with the improvement of the injection efficiency. On the other hand, in the conventional device, the average is 500 μm.
Although cracks occurred at approximately regular intervals, only a few cracks were observed around the sample in the device manufactured in this example. The above-mentioned effects were similarly confirmed on different kinds of substrates such as sapphire in addition to GaN.

Example 5 A laser device was fabricated on a (0001) plane GaN substrate as shown below. In this embodiment, the first n-type AlGaN
Cladding layer and second n-type AlGaN cladding layer
AlGaN provided with a mold cladding layer and placed between them
When the growth temperature of the dislocation blocking layer was 1050 ° C. and the carbon concentration of the dislocation blocking layer was changed, the dislocation density penetrating the active layer and the device characteristics were measured. The manufacturing method and the result will be described with reference to FIG. 1, FIG. 8 and FIG.

Using the (0001) plane GaN substrate, the device structure shown in FIG. However, in the element shown in FIG.
N-type A1 _0.15 Ga _0.85 N cladding layers 103 and 10
5 were set to 0.2 μm and 0.3 μm, respectively. Further, the thickness of the dislocation blocking layer 104 disposed between the first and second n-type A1 _0.15 Ga _0.85 N cladding layers is set to 0.1.
On the other hand, while growing the dislocation blocking layer,
H ₄ was supplied to change the carbon concentration in the dislocation blocking layer. Here, the first and second n-type cladding layers may or may not contain carbon, but the concentration when carbon is contained is 10 ²⁰
Must be lower than cm ^-3 . This is because excess carbon becomes a new dislocation source. The carbon concentration after growth was measured by SIMS.

FIG. 8 shows the relationship between the carbon concentration of the AlGaN dislocation blocking layer and
4 shows the relationship with the dislocation density penetrating the active layer. Carbon concentration
10¹⁴cm^-3Lower than area and 10²⁰cm^-3Over
It can be seen that the dislocation density is high in the region where versus
Illuminating 10¹⁴cm^-3More than 10 ²⁰cm^-3In the following areas
The phase density is significantly reduced. Carbon concentration of 10¹⁴cm ^-3
If lower, dislocations are effectively blocked in the dislocation blocking layer.
Can't form enough carbon clusters
Dislocations generated from the first cladding layer are
It reaches the active layer. Conversely 10²⁰cm^-3More than charcoal
At elemental concentration, carbon exists in a state close to the composition of the host crystal
This disturbs the periodicity of the crystal,
Element clusters are a new dislocation source, lowering the crystallinity of the upper layer.
Let it down. From the above results, the carbon content of the dislocation blocking layer
Concentration 10¹⁴From 10²⁰cm^-3When, dislocation propagation blocking effect
It turns out that the fruit is big. Therefore, the present invention is applied.
In order to maximize its effect,
The concentration of carbon added to the¹⁴-10²⁰cm^-3When
It is desirable to do.

FIG. 9 shows the relationship between the driving voltage of the device and the threshold current density with respect to the carbon concentration of the dislocation blocking layer. In the same figure, a black circle represents a threshold current density, and a black triangle represents a drive voltage. It can be seen that the threshold current density changes according to the relationship between the carbon concentration and the dislocation density. Carbon concentration of 10 ¹⁴ cm ^-3 or more and 10 ²⁰
The threshold current density cm ^-3 or less in the region as compared to less than 600A / cm ^2, less than 10 ¹⁴ cm ^-3 and 10 ²⁰ cm
In region exceeding ^-3 1000A from 800A / cm ² /
cm ² or more and 10 ¹⁴ cm ^-3 or more and 10 ²⁰ c
It can be confirmed that the dislocation blocking effect by the dislocation blocking layer is large at a carbon concentration of m ⁻³ or less. Since the driving voltage is hardly affected by the dislocation, the fluctuation with respect to the carbon concentration is small. Also,
The carbon concentration of the AlGaN dislocation blocking layer is 10 ¹⁴ cm ^-3 or more 1
At 0 ²⁰ cm ^-3 or less, cracks on the element surface were greatly reduced. Due to this effect, the yield in the device forming process is greatly improved.

The above tendency is the same on different kinds of substrates such as sapphire, and shows that the effects of the present invention appear regardless of the substrate.

Example 6 A laser device was manufactured on a (0001) plane GaN substrate as shown below. In this embodiment, the first n-type AlGa
Providing two n-type cladding layers, an N-type cladding layer and a second n-type AlGaN cladding layer,
The growth temperature of the aN dislocation blocking layer was changed from 500 ° C. to 1050 ° C. The production, the relationship between the concentration of carbon incorporated in the dislocation blocking layer, the dislocation density penetrating the active layer, and the device characteristics will be described with reference to FIGS. 1, 10, and 11. FIG.

Using the (0001) plane GaN substrate, the element structures shown in FIG. 1 are sequentially stacked according to the procedure described in the first embodiment. However, in the element shown in FIG.
N-type A1 _0.15 Ga _0.85 N cladding layers 103 and 10
5 were set to 0.2 μm and 0.3 μm, respectively. Here, the first and second n-type cladding layers may or may not include carbon, but the concentration when carbon is included must be lower than 10 ²⁰ cm ⁻³ . this is,
This is because excess carbon becomes a new dislocation source. Further, in order to unify the thickness of the A1 _0.15 Ga _0.85 N dislocation blocking layer 104 disposed between the first and second n-type Al _0.15 Ga _0.85 N cladding layers to 0.1 μm, the thickness of each of the Al. The growth time was increased or decreased to respond.

In this embodiment, when growing the dislocation blocking layer, CH ₄
Not supply. Instead, by reducing the group V source during growth and maintaining the ratio of the group V source to the group III source at 3000 or less, the elimination of alkyl groups from the group III organometallic source due to the catalytic effect of the group V source is suppressed. Then, under the growth conditions in which carbon is easily incorporated into the dislocation blocking layer, carbon addition was performed using an alkyl group as a raw material. The concentration of carbon incorporated in the dislocation blocking layer was measured by SIMS.

With respect to the growth temperature of the dislocation blocking layer, V / II
FIG. 10 shows the result of plotting the concentration of incorporated carbon and the density of dislocations penetrating the active layer when the I ratio is 3000. In the figure, the black circles represent the dislocation density, and the black triangles represent the carbon concentration. Under the growth conditions in which the V / III ratio exceeds 3000, the catalytic action of the group V raw material becomes remarkable, and the effect of carbon addition derived from the alkyl group is significantly reduced. Therefore, it is necessary to supply CH ₄ or the like as a carbon source. There is. As the growth temperature of the dislocation blocking layer increases from 500 ° C. to around 750 ° C., the concentration of carbon contained decreases. In the temperature range where the V / III ratio is 3000 or less and 750 ° C. or less, since the catalytic action of the group V raw material is small, the methyl group (CH ₃ ) which is the alkyl group of TMG which is the Ga raw material
The bond between Ga and Ga is not broken and is taken into the solid phase in an undecomposed state, so that the amount of carbon in the solid phase increases. Especially 5
This tendency is remarkable at around 00 ° C., but as the growth temperature rises, separation of methyl groups by thermal energy progresses, and the carbon concentration decreases to a growth temperature of about 750 ° C. 75
Between 0 ° C. and 950 ° C., although the concentration of undecomposed Ga-methyl group in the gas phase decreases for the above-described reason, the gas phase reaction between ammonia and TMG increases and Ga contributing to crystal growth decreases. At the same time, the growth rate of the dislocation blocking layer also decreases. Therefore, when compared with the growth rate of the dislocation blocking layer, the state becomes equivalent to a state in which the concentration of Ga-methyl group is increased, and the amount of carbon incorporated into the solid phase is slightly increased. 950
At a growth temperature higher than ° C., the thermal energy obtained by TMG increases and the separation of methyl groups becomes almost 100%, so that the amount of carbon taken in decreases regardless of the growth rate.
It can be seen that the density of threading dislocations changes with such a change in carbon concentration. In the region from 500 ° C. to 750 ° C., the threading dislocation density gradually increases as the carbon concentration decreases,
In a region exceeding 50 ° C., the degree of increase in the threading dislocation density is large corresponding to the decrease in the carbon concentration. Since the carbon derived from the organic metal decreases as the growth temperature increases, it is necessary to supply CH ₄ or the like to compensate for the amount of carbon taken into the solid phase. In particular, in the region where the growth temperature exceeds 1050 ° C., even when the dislocation blocking layer is provided, the structure becomes close to the conventional structure in which the cladding layer is not divided, and unless a separate carbon source is supplied, the quality of the active layer deteriorates. , Cracks occur. Therefore,
At a high temperature of 1000 ° C. or higher for actually growing the AlGaN cladding layer, it is necessary to separately supply a carbon source. In this case, as the carbon raw material, in addition to CH ₄ , a carbon compound represented by the general formula C _n H _{2 (n + 1)} , C (C _n H _{2n + 1} ) ₄
May be used.

As can be seen from FIG. 10, at a growth temperature exceeding 1100 ° C., the threading dislocation density becomes extremely high. Therefore, the growth temperature of the dislocation blocking layer is desirably 1100 ° C. or lower. At a growth temperature of less than 500 ° C., the dislocation blocking layer becomes amorphous, and the continuity of the crystal between the first and second claddings is undesirably broken. Therefore, the growth temperature of the dislocation blocking layer is 500 ° C. or higher and 1100 ° C.
It is desirable that the temperature is not more than ° C.

FIG. 11 shows the relationship between the growth temperature of the AlGaN dislocation blocking layer, the driving voltage of the laser element, and the oscillation threshold current. In the figure, a black circle indicates a threshold current density, and a black triangle indicates a drive voltage. It can be seen that the drive voltage hardly changes, but the threshold current density changes depending on the growth temperature. Between 500 ° C. and 750 ° C., the threshold current density shows a substantially constant threshold current density as the temperature rises. Over 750 ° C, 950
In the region around ° C., the threshold current density greatly increases.
Above 950 ° C., the increase in the threshold current density is small. The behavior of the threshold current density with respect to the growth temperature of the dislocation blocking layer corresponds well to changes in the carbon concentration in the dislocation blocking layer and the threading dislocation density in the active layer. That is, the threading dislocation density and the threshold current density decrease in a region where the carbon concentration is high, and conversely, both the threading dislocation density and the threshold current density increase when the carbon concentration is low. The reason for the small change in the driving voltage is that p
This is because the voltage is determined by the resistance of the mold layer, and the activation rate of the p-type carrier is not significantly affected by the dislocation density.

The above tendency is the same even when an element structure is formed on another substrate such as sapphire, and the effect of the present invention appears regardless of the substrate.

Example 7 A laser device was manufactured on a (0001) plane GaN substrate.
In this embodiment, the first n-type AlGaN cladding layer and the second
Are formed, and the growth temperature of the dislocation blocking layer disposed between them is 1050 ° C., and the total thickness of the first and second n-type AlGaN cladding layers ( Was fixed at 0.5 μm, and the thickness of the dislocation blocking layer was changed. The production and the result of measuring the element characteristics and the dislocation density penetrating the active layer will be described with reference to FIGS. 1, 12, and 13. FIG.

Example using (0001) plane GaN substrate
1 was formed in the same manner as in Example 1. However,
In the device shown in FIG. 1, first and second n-type A1_0.15
Ga _0.85The total thickness of the N cladding layers 103 and 105 is
Fixed to 0.5 μm, each layer thickness 0.2 μm
It was set to 0.3 μm. Here, the first and second n-type
The cladding layer may or may not contain carbon,
Concentration when containing 10²⁰cm^-3Must be lower
No. This is because excess carbon becomes a new dislocation source.
It is. Also, the first and second n-type A1_0.15Ga_0.85
A1 placed between N cladding layers_0.15Ga_0.85N dislocation block
The thickness of the stop layer 104 is changed in the range of 10 nm to 1 μm.
I let you. AlGaN dislocation blocking layer thickness changes growth time
Controlled by that. Also, when growing the dislocation blocking layer, CH_FourSupply
To make the solid phase carbon concentration 10¹⁹cm^-3Unified. That
The general formula C_nH_{2 (n + 1)}A carbon compound represented by the formula: C (C_n
H_{2n + 1})_FourMay be used. growth
The subsequent carbon concentration was confirmed by SIMS.

FIG. 12 shows the relationship between the thickness of the AlGaN dislocation blocking layer and the dislocation density penetrating the active layer. The figure shows that the dislocation blocking effect is large when the thickness of the dislocation blocking layer is 40 nm or more and 0.7 μm or less. In the dislocation blocking layer of less than 40 nm, the carbon cluster density in the thickness direction is not sufficient,
It is considered that dislocations generated from the first n-type AlGaN cladding penetrate between carbon clusters and reach the active layer. If the thickness of the dislocation blocking layer exceeds 0.7 μm, the strain relaxation by the carbon cluster exceeds the limit, so that the dislocation blocking layer itself can be a dislocation source. As shown by a broken line in FIG. 12, the dislocation density increases sharply for a thickness of less than 40 nm or more than 7 μm. Therefore, the thickness of the dislocation blocking layer for exhibiting the effect of the present invention is desirably 40 nm or more and 0.7 μm or less.

FIG. 13 shows the relationship between the drive voltage and the threshold current density with respect to the thickness of the AlGaN dislocation blocking layer. In the figure, a black circle indicates a threshold current density, and a black triangle indicates a drive voltage.
As in Examples 5 to 7, the threshold current density changes according to the dislocation density. That is, from 40 nm to 0.7
When a μm dislocation blocking layer was applied, a decrease in threshold current density was confirmed. As indicated by the broken line in FIG. 13, the threshold current density increases sharply at boundaries of less than 40 nm and 0.7 μm, corresponding to the dislocation density. The above tendency is the same on other types of substrates, such as sapphire, indicating that the present invention is effective regardless of the substrate.

Example 8 A laser device was manufactured on a (0001) plane GaN substrate.
In this embodiment, the first n-type AlGaN cladding layer and the second
Two n-type cladding layers of the n-type AlGaN cladding layer, and the growth temperature of the dislocation blocking layer disposed between them is set to 1
050 ° C., the thickness of the dislocation blocking layer is fixed at 0.1 μm, and the total thickness of the first and second AlGaN layers is 1 μm.
, While changing the thickness of each n-type cladding layer. The production and the results of measuring the device characteristics and the dislocation density penetrating the active layer will be described with reference to FIGS. 1, 14 and 15 by using a (0001) plane GaN substrate and performing the same procedure as in Example 1. The element structure shown in FIG. 1 was formed. However, while fixing the total thickness of the first and second n-type Al _{0. 15} Ga _0.85 N cladding layer 103 and 105 to 1μm in the device shown in FIG. 1, the thickness of the first n-type AlGaN cladding layer From 0.1 μm to 0.9 μm
m. First and second n-type AlGaN
Since the total thickness of the cladding layer is fixed at 1 μm,
The thickness of the second n-type AlGaN cladding layer is the first n-type AlGaN cladding layer.
It varies between 0.9 μm and 0.1 μm according to the thickness of the lGaN layer. The thickness of each cladding layer was controlled by changing the growth time. Here, the first and second n
The mold cladding layer may or may not contain carbon, but if it does, the concentration must be less than 10 ²⁰ cm ⁻³ . This is because excess carbon becomes a new dislocation source. During the growth of the dislocation blocking layer, CH ₄ was supplied to unify the solid phase carbon concentration to 10 ¹⁹ cm ^-3 . At that time, the carbon compound represented by the general formula _{C n H 2 (n + 1} ), C (C n H 2n + 1)
_The carbon compound represented by ₄ may be used. The carbon concentration after growth was confirmed by SIMS.

The thickness of the first n-type AlGaN cladding layer
FIG. 14 shows a change in threading dislocation density. Normal element
Less than one dislocation that can exist in the current-carrying region of the element
Then, the effect of dislocation can be neglected in practical use.
The corresponding dislocation density is 5 × 10^Fourcm^-2About. Dislocation blocking
First n-type AlGaN cladding layer located below the stop layer
Is less than 0.7 μm, 5 × 10^Fourcm^-2below
While the dislocation density is maintained, the broken line in FIG.
As shown, at a thickness exceeding 0.7 μm, 10 ^Fivecm^-3
Order, and the dislocation density tends to increase rapidly
is there. This is the thickness of the first n-type AlGaN cladding layer.
Exceeds the limit that can be stopped by the dislocation blocking layer because
This is because dislocations have occurred. Therefore, the first n-type Al
The GaN cladding layer should be less than 0.7μm thick
desirable. In addition, the second n-type AlGaN cladding layer
The same can be said. That is, by the dislocation blocking layer
Even when dislocation propagation from the lower layer is blocked,
The second n-type AlGaN cladding layer located above the stop layer is
If thick, a new n-type AlGaN cladding layer
Since dislocations occur, the thickness is, for example, 0.2 μm
It is desirable that: Or, relative to the element design,
When a thick n-type AlGaN cladding layer is required
Is effective in dislocation prevention by arranging multiple dislocation blocking layers.
Propagation can be prevented.

FIG. 15 shows the relationship between the drive voltage and the threshold current density with respect to the thickness of the first n-type AlGaN cladding layer. In the figure, a black circle indicates a threshold current density, and a black triangle indicates a drive voltage. As in Examples 5 to 7, the threshold current density changes according to the dislocation density. First n-type AlGa
When the thickness of the N cladding layer was 0.7 μm or less, a remarkable decrease in threshold current density was confirmed. Conversely, as indicated by the broken line in FIG. 15, it can be seen that the threshold current density sharply increases at a thickness exceeding 0.7 μm. This tendency is shown in FIG.
Corresponds to the dislocation density. The above tendency is the same for other types of substrates, such as sapphire, indicating that the present invention is effective regardless of the substrate.

Example 9 A laser device was manufactured on a (0001) plane GaN substrate.
In this embodiment, the first n-type AlGaN cladding layer and the second
Two n-type cladding layers of the n-type AlGaN cladding layer are provided, and the growth temperature of the dislocation blocking layer disposed therebetween is set to 1
050 ° C., the thickness of the dislocation blocking layer is fixed to 0.1 μm, and the thicknesses of the first and second AlGaN cladding layers are set to 0.2 μm and 0.3 μm, respectively. changed. The production of the device and the results of measuring the device characteristics and the dislocation density penetrating the active layer will be described with reference to FIGS. 1, 16, 17, 18, and 19. FIG.

Using a (0001) plane GaN substrate, an element structure shown in FIG. 1 was manufactured in the same procedure as in Example 1.
However, in the element shown in FIG. 1, the first and second n-type A
1 _{0. 15} Ga _0.85 N thickness each 0.2μm cladding layer 103 and 105, the 0.3 [mu] m, a dislocation-blocking layer 10
4 was fixed to 0.1 μm, and the composition of the dislocation blocking layer was sequentially changed. Here, the first and second n-type cladding layers may or may not include carbon, but the concentration when carbon is included must be lower than 10 ²⁰ cm ⁻³ . This is because excess carbon becomes a new dislocation source. The composition of the dislocation blocking layer was controlled by supplying TMA and TMI and changing their amounts. Also, when growing the dislocation blocking layer, C
H ₄ was supplied to unify the solid phase carbon concentration to 10 ¹⁹ cm ^-3 . At that time, the carbon compound represented by the general formula _{C n H 2 (n + 1} ), may be used carbon compound represented by _{C (C n H 2n + 1} ) 4. The carbon concentration after growth was confirmed by SIMS.
FIGS. 16 and 17 show changes in the threading dislocation density with respect to the A1 composition and the In composition of the dislocation blocking layer. It can be seen that the threading dislocation density does not change significantly with the composition change of the dislocation blocking layer. This indicates that the dislocation inhibiting effect does not depend on the composition but on the concentration of carbon contained in the layer. In fact, when carbon was added at a concentration of less than 10 ¹⁴ cm ^-3 or more than 10 ²⁰ cm ^-3 , the threading dislocation density increased to 10 ⁸ cm ^-2 or more in all compositions.

FIGS. 18 and 19 show the relationship between the drive voltage and the threshold current density with respect to the composition of the dislocation blocking layer. In the plan view, a black circle indicates a threshold current density, and a black triangle indicates a drive voltage. Like the threading dislocation density, the threshold current density is almost constant regardless of the composition of the dislocation blocking layer. However, if carbon is 10 ¹⁴ c
At a concentration lower than m ^-3 or higher than 10 ²⁰ cm ^-3 , the threshold current density increased to 1000 A / cm ² or more. The above tendency is the same for other types of substrates, such as sapphire, indicating that the present invention is effective regardless of the substrate.

Example 10 A laser device was manufactured on a (0001) plane GaN substrate.
In this embodiment, the n-type cladding layer is made of a GaN thin film and AlN.
A strained superlattice (SLS) structure in which thin films are alternately stacked,
Carbon was added to the GaN layer in the SLS. The structure of the device and the distribution of carbon will be described with reference to FIGS. 1, 20, and 21. FIG.

Using a (0001) plane GaN substrate, an element structure shown in FIG. 20 was manufactured in the same procedure as in Example 1. However, in the same figure, the n-type cladding layer (2003)
Is a 0.5-nm-thick AlN which is made n-type by adding silicon.
Layer 2003a and 4.5 nm thick GaN layer 2003b
Have an SLS structure alternately stacked. The overall thickness of the n-type cladding layer 2003 is 0.5 μm,
GaN is repeated 100 times and stacked. Ga
Due to the ratio of the layer thicknesses of N and AlN, the average Al composition ratio of the entire n-type cladding layer is 0.1. S according to the present embodiment
In LS, the GaN layer 2003b contains carbon and functions as a dislocation element layer. Other structures are the same as those of the element shown in FIG.

For comparison, a device having a normal SLS clad containing no carbon in the GaN layer was manufactured.

FIG. 21 shows the carbon concentration distribution of these devices. The element A includes carbon in the SLS, and the element B does not include carbon in the SLS. In the ordinary device B, the carbon concentration is below the detection limit, whereas in the SLS clad device A including the dislocation blocking layer, the carbon concentration of the AlN layer in the SLS is 10 ¹⁴ cm ⁻³ and the dislocation blocking layer is GaN. The carbon concentration of the layer has a regular concentration distribution of 10 ¹⁹ cm ^-3 . When the element A is energized, the drive voltage is 4.5.
At V, the oscillation threshold current density showed good characteristics of 420 A / cm ² , but when a normal SLS element B was energized, the oscillation threshold current showed a high value of 550 A / cm ² at a drive voltage of 5.1 V, and SLS The effect of the dislocation blocking layer was also confirmed in the structure.

The composition, thickness and repetition period of each layer constituting the SLS can be arbitrarily adjusted so as to satisfy the average composition of the entire SLS required from the device design. The carbon concentration is 10 ¹⁴ irrespective of the composition of each layer.
The element characteristics can be improved by alternately stacking a dislocation blocking layer having a size of not less than cm ^{-3 and not} more than 10 ²⁰ cm ^-3 and a layer having a carbon concentration of less than 10 ¹⁴ cm ^-3 .

The above tendency is the same for other kinds of substrates such as sapphire, and it shows that the present invention is effective regardless of the substrate. Further, as a carbon source added to the dislocation blocking layer, a carbon compound represented by the general formula C _n H _{2 (n + 1)} ,
A carbon compound represented by (C _n H _{2n + 1} ) ₄ can be used.

[0066]

As described above, according to the present invention, it is possible to reduce the dislocation density penetrating the light emitting layer in the light emitting device and reduce the cracks generated on the device surface. According to the present invention, by providing the dislocation blocking layer containing carbon, for example, the threshold current density of the laser device can be reduced. Further, by the stress relaxation by the dislocation blocking layer, the occurrence of cracks on the element surface can be prevented, and the yield of element production can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a laser device according to the present invention.

FIG. 2 is a schematic sectional view showing a conventional element structure.

FIG. 3 is a schematic sectional view showing another example of the laser device according to the present invention.

FIG. 4 is a schematic cross-sectional view showing a conventional structure formed on a sapphire substrate.

FIG. 5 is a schematic sectional view showing another example of the laser device according to the present invention.

FIG. 6 is a schematic sectional view showing another example of the laser device according to the present invention.

FIG. 7 is a schematic diagram of a crystal growth apparatus used in an example.

FIG. 8 is a diagram showing the relationship between the carbon concentration of a dislocation blocking layer and the dislocation density penetrating the active layer.

FIG. 9 is a diagram showing the relationship between the carbon concentration of the dislocation blocking layer, the oscillation threshold current of the device, and the drive voltage.

FIG. 10 is a graph showing the relationship between the concentration of carbon incorporated in a dislocation stop layer and the dislocation density penetrating an active layer.

FIG. 11 is a diagram showing a relationship between a growth temperature of a dislocation blocking layer, an oscillation threshold current of a laser element, and a driving voltage.

FIG. 12 is a diagram showing the relationship between the thickness of a dislocation blocking layer and the density of dislocations penetrating an active layer.

FIG. 13 is a diagram showing a relationship between the thickness of a dislocation blocking layer, an oscillation threshold current, and a driving voltage.

FIG. 14 is a diagram showing the relationship between the thickness of the first n-type AlGaN cladding layer and the threading dislocation density.

FIG. 15 is a diagram showing a relationship between the thickness of a first n-type AlGaN cladding layer, an oscillation threshold current, and a drive voltage.

FIG. 16 is a diagram showing the relationship between the A1 composition ratio of the dislocation blocking layer and the dislocation density penetrating the active layer.

FIG. 17 is a diagram showing the relationship between the In composition ratio of the dislocation blocking layer and the dislocation density penetrating the active layer.

FIG. 18 is a diagram showing the relationship between the A1 composition ratio of the dislocation blocking layer, the oscillation threshold current, and the driving voltage.

FIG. 19 is a diagram showing a relationship between an In composition ratio of a dislocation blocking layer, an oscillation threshold current, and a driving voltage.

FIG. 20 is a schematic sectional view showing another example of the device according to the present invention.

FIG. 21 is a diagram showing a carbon concentration distribution in a thickness direction of an n-type SLS clad.

[Explanation of symbols]

101 (0001) plane n-type GaN substrate, 102 n-type GaN layer, 103 first n-type Al _0.15 Ga _0.85 N cladding layer, 104 carbon-added dislocation blocking layer, 105 second n
Type A1 _0.15 Ga _0.85 N cladding layer, 106 n-type GaN
Light guide layer, 107 InGaN multiple quantum well active layer,
108 AlGaN block layer, 109 p-type GaN light guide layer, 110 p-type Al _0.15 Ga _0.85 N clad layer,
111p-type GaN layer, 112p-type GaN contact layer, 113 insulating film, 114p-type electrode, 115n-type electrode, 201 (0001) plane n-type GaN substrate, 202n
-Type GaN layer, 203 n-type Al _0.15 Ga _0.85 N cladding layer, 204 n-type GaN light guide layer, 205 InGa
N multiple quantum well active layer, 206 AlGaN block layer, 207 p-type GaN light guide layer, 208 p-type Al
_0.15 Ga _0.85 N cladding layer, 209 p-type GaN layer, 2
10 p-type GaN contact layer, 211 insulating film, 212
p-type electrode, 213 n-type electrode, 301 (0001)
Plane sapphire substrate, 302 GaN buffer layer, 303
n-type GaN layer, 304 first n-type Al _0.15 Ga _0.85
N clad layer, 305 carbon-added dislocation blocking layer, 306 second n-type Al _0.15 Ga _0.85 N clad layer, 307 n-type GaN light guide layer, 308 InGaN multiple quantum well active layer, 309 AlGaN block layer, 310 p-type Ga
N light guide layer, 311 p-type Al _0.15 Ga _0.85 N clad layer, 312 p-type GaN layer, 313 p-type GaN contact layer, 314 insulating film, 315 p-type electrode, 316 n
Type electrode, 401 (0001) plane sapphire substrate, 40
2GaN buffer layer, 403 n-type GaN layer, 404
n-type Al _0.15 Ga _0.85 N cladding layer, 405 n-type Ga
N light guide layer, 406 InGaN multiple quantum well active layer, 407 AlGaN block layer, 408 p-type Ga
N light guide layer, 409 p-type Al _0.15 Ga _0.85 N clad layer, 410 p-type GaN layer, 411 p-type GaN contact layer, 412 insulating film, 413 p-type electrode, 414
n-type electrode, 501 (0001) plane n-type GaN substrate,
502 n-type GaN layer, 503 n-type Al _0.15 Ga _0.85
N cladding layer, 504 carbon-added dislocation blocking layer, 505
n-type GaN optical guide layer, 506 InGaN multiple quantum well active layer, 507 AlGaN block layer, 508 p
-Type GaN optical guide layer, 509 p-type Al _0.15 Ga _0.85 N
Cladding layer, 510 p-type GaN layer, 511 p-type Ga
N contact layer, 512 insulating film, 513 p-type electrode, 5
14 n-type electrode, 601 (0001) plane n-type GaN substrate, 602 n-type GaN layer, 603 n-type Al _0.15 Ga
_0.85 N cladding layer, 604 n-type GaN optical guiding layer, 6
05 carbon-added dislocation blocking layer, 606 InGaN multiple quantum well active layer, 607 AlGaN block layer, 608
p-type GaN optical guide layer, 609 p-type Al _0.15 Ga
_0.85 N cladding layer, 610 p-type GaN layer, 611 p
GaN contact layer, 612 insulating film, 613 p-type electrode, 614 n-type electrode, 701 substrate, 702 carbon susceptor, 703 quartz reaction tube, 704 raw material inlet, 705 exhaust port, 706 NH ₃ , 707 Si
_{H 4, 708 CH 4, 709a} TMG, 709b TM
A, 709c TMI, 709d Cp ₂ Mg, 710
Mass flow controller, 12001 (0001)
Plane n-type GaN substrate, 2002 n-type GaN layer, 2003
n-type SLS cladding layer, 2003a n-type AlN layer,
2003b Carbon-doped GaN dislocation blocking layer, 2004n
-Type GaN optical guide layer, 2005 InGaN multiple quantum well active layer, 2006 AlGaN block layer, 2007
p-type GaN optical guide layer, 2008 p-type Al _0.15 Ga
_0.85 N cladding layer, 2009 p-type GaN layer, 2010
p-type GaN contact layer, 2011 insulating film, 2012
p-type electrode, 2013 n-type electrode.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yuzo Tsuda 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Jun Ogawa 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside (72) Inventor Masahiro Araki 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Japan Inside Sharp Corporation (72) Inventor Teruyoshi Takakura 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Sharp Corporation F Terms (reference) 5F073 AA11 AA45 AA51 AA55 AA74 CA07 CB05 CB07 CB19 DA05 DA35 EA29

Claims (9)

[Claims] 1. A nitride semiconductor light emitting device having a structure in which a plurality of layers made of a nitride semiconductor are formed on a substrate, wherein a nitride layer is formed between the light emitting layer of the plurality of layers and the substrate. A nitride semiconductor light-emitting device, comprising a dislocation blocking layer made of a nitride semiconductor and containing carbon. 2. A first layer made of a nitride semiconductor between the light-emitting layer and the substrate, and a first layer made of a nitride semiconductor containing an element different from the first layer, and A plurality of second layers close to the light emitting layer are provided;
The nitride semiconductor light emitting device according to claim 1, wherein the dislocation blocking layer is provided between the plurality of second layers. 3. The nitride semiconductor light emitting device according to claim 2, wherein the thickness of said second layer is 0.7 μm or less. 4. A first layer made of a nitride semiconductor between the light emitting layer and the substrate, and a first layer made of a nitride semiconductor containing an element different from the first layer, and A second layer close to the light emitting layer is provided, and the dislocation blocking layer is provided between the second layer and the light emitting layer or in the second layer. The nitride semiconductor light emitting device according to claim 1, wherein 5. The semiconductor device according to claim 2, wherein the first layer is made of a nitride semiconductor containing no Al, and the second layer is made of a nitride semiconductor containing Al. 2. The nitride semiconductor light emitting device according to claim 1. 6. The dislocation blocking layer according to claim 1, wherein said carbon is 10 ¹⁴ /
The nitride semiconductor light emitting device according to any one of claims 1 to 5, wherein the nitride semiconductor light emitting device is contained at a concentration of not less than cm ^{3 and not} more than 10 ²⁰ / cm ³ . 7. The dislocation blocking layer has a thickness of 40 nm or more and 0.7 or less.
characterized by having a thickness of less than or equal to μm.
7. The nitride semiconductor light emitting device according to any one of 6. 8. A nitride semiconductor constituting the nitride semiconductor light emitting device has the general formula _{In x Ga y Al 1- (x} + y) N (0 ≦
The nitride semiconductor light emitting device according to claim 1, wherein the nitride semiconductor is a nitride semiconductor represented by x ≦ 1, 0 ≦ x + y ≦ 1). 9. The method for manufacturing a nitride semiconductor light emitting device according to claim 1, comprising a nitride semiconductor including the dislocation blocking layer and the light emitting layer on a substrate. A manufacturing method, comprising a step of forming a plurality of layers, wherein the dislocation blocking layer is grown at a temperature of 500 ° C. or more and 1100 ° C. or less.